alice.tuprolog

Class Var

java.lang.Object

alice.tuprolog.Term

alice.tuprolog.Var

All Implemented Interfaces:

Serializable

public class Var
extends Term

This class represents a variable term. Variables are identified by a name (which must starts with an upper case letter) or the anonymous ('_') name.

See Also:

Term, Serialized Form

Field Summary

Fields inherited from class alice.tuprolog.Term

FALSE, TRUE

Constructor Summary

Constructors

Constructor and Description
Var() Creates an anonymous variable This is equivalent to build a variable with name _
Var(String n) Creates a variable identified by a name.

Method Summary

Methods

Modifier and Type	Method and Description
Term	copy(AbstractMap vMap, AbstractMap substMap) Gets a copy of this variable.
Term	copy(AbstractMap vMap, int idExecCtx) Gets a copy of this variable.
void	free() De-unify the variable
static void	free(List varsUnified) De-unify the variables of list
String	getName() Gets the name of the variable
String	getOriginalName() Gets the name of the variable
Term	getTerm() Gets the term which is referred by the variable.
boolean	isAnonymous() Tests if this variable is ANY
boolean	isAtom() is this term a prolog (alphanumeric) atom?
boolean	isAtomic() is this term a constant prolog term?
boolean	isBound() Tests if this variable is bound
boolean	isCompound() is this term a prolog compound term?
boolean	isEmptyList() is this term a null term?
boolean	isEqual(Prolog mediator, Term t) Tests if this term is (logically) equal to another
boolean	isGreater(Prolog mediator, Term t) Gets a copy of this variable
boolean	isGround() is this term a ground term?
boolean	isList() is this term a prolog list?
boolean	isNumber() is this term a prolog numeric term?
boolean	isStruct() is this term a struct?
boolean	isVar() is this term a variable?
long	resolveTerm(long count) Resolve the occurence of variables in a Term
String	toString() Gets the string representation of this variable.
String	toStringFlattened() Gets the string representation of this variable, providing the string representation of the linked term in the case of bound variable
boolean	unify(Prolog mediator, List vl1, List vl2, Term t) var unification.

Methods inherited from class alice.tuprolog.Term

copyGoal, copyResult, createTerm, createTerm, equals, getIterator, iteratedGoalTerm, match, parse, parse, resolveTerm, unify

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Var

public Var(String n)
    throws InvalidTermException

Creates a variable identified by a name. The name must starts with an upper case letter or the underscore. If an underscore is specified as a name, the variable is anonymous.

Parameters:

n - is the name

Throws:

InvalidTermException - if n is not a valid name

Var

public Var()

Creates an anonymous variable This is equivalent to build a variable with name _

Method Detail

copy

public Term copy(AbstractMap vMap,
        int idExecCtx)

Gets a copy of this variable. if the variable is not present in the list passed as argument, a copy of this variable is returned and added to the list. If instead a variable with the same time identifier is found in the list, then the variable in the list is returned.

Specified by:

copy in class Term

idExecCtx - Execution Context identifier

copy

public Term copy(AbstractMap vMap,
        AbstractMap substMap)

Gets a copy of this variable.

Specified by:

copy in class Term

free

public void free()

De-unify the variable

Specified by:

free in class Term

free

public static void free(List varsUnified)

De-unify the variables of list

getName

public String getName()

Gets the name of the variable

getOriginalName

public String getOriginalName()

Gets the name of the variable

getTerm

public Term getTerm()

Gets the term which is referred by the variable. For unbound variable it is the variable itself, while for bound variable it is the bound term.

Specified by:

getTerm in class Term

isNumber

public boolean isNumber()

Description copied from class: Term

is this term a prolog numeric term?

Specified by:

isNumber in class Term

isStruct

public boolean isStruct()

Description copied from class: Term

is this term a struct?

Specified by:

isStruct in class Term

isVar

public boolean isVar()

Description copied from class: Term

is this term a variable?

Specified by:

isVar in class Term

isEmptyList

public boolean isEmptyList()

Description copied from class: Term

is this term a null term?

Specified by:

isEmptyList in class Term

isAtomic

public boolean isAtomic()

Description copied from class: Term

is this term a constant prolog term?

Specified by:

isAtomic in class Term

isCompound

public boolean isCompound()

Description copied from class: Term

is this term a prolog compound term?

Specified by:

isCompound in class Term

isAtom

public boolean isAtom()

Description copied from class: Term

is this term a prolog (alphanumeric) atom?

Specified by:

isAtom in class Term

isList

public boolean isList()

Description copied from class: Term

is this term a prolog list?

Specified by:

isList in class Term

isGround

public boolean isGround()

Description copied from class: Term

is this term a ground term?

Specified by:

isGround in class Term

isAnonymous

public boolean isAnonymous()

Tests if this variable is ANY

isBound

public boolean isBound()

Tests if this variable is bound

resolveTerm

public long resolveTerm(long count)

Resolve the occurence of variables in a Term

Specified by:

resolveTerm in class Term

Parameters:

count - new starting time count for resolving process

Returns:

the new time count, after resolving process

unify

public boolean unify(Prolog mediator,
            List vl1,
            List vl2,
            Term t)

var unification.

First, verify the Term eventually already unified with the same Var if the Term exist, unify var with that term, in order to handle situation as (A = p(X) , A = p(1)) which must produce X/1.

If instead the var is not already unified, then:

if the Term is a var bound to X, then try unification with X so for example if A=1, B=A then B is unified to 1 and not to A (note that it's coherent with chronological backtracking: the eventually backtracked A unification is always after backtracking of B unification.

if are the same Var, unification must succeed, but without any new bindings (to avoid cycles for extends in A = B, B = A)

if the term is a number, then it's a success and new link is created (retractable by means of a code)

if the term is a compound, then occur check test is executed: the var must not appear in the compound ( avoid X=p(X), or p(X,X)=p(Y,f(Y)) ); if occur check is ok then it's success and a new link is created (retractable by a code)

Specified by:

unify in class Term

Parameters:

mediator - TODO

vl1 - Vars unified in myself

vl2 - Vars unified in term t

isGreater

public boolean isGreater(Prolog mediator,
                Term t)

Gets a copy of this variable

Specified by:

isGreater in class Term

Parameters:

mediator - TODO

isEqual

public boolean isEqual(Prolog mediator,
              Term t)

Description copied from class: Term

Tests if this term is (logically) equal to another

Specified by:

isEqual in class Term

Parameters:

mediator - TODO

toString

public String toString()

Gets the string representation of this variable. For bounded variables, the string is /.

Overrides:

toString in class Object

toStringFlattened

public String toStringFlattened()

Gets the string representation of this variable, providing the string representation of the linked term in the case of bound variable